Antiferromagnetic complexes with metalmetal bonds: XVIII. The influence of electronic factors on geometry of heterometallospirane clusters. Molecular structure and magnetic properties of Cp 2Cr 2(μ-SCMe 3)(μ 3-S) 2M(μ 3-S) 2Fe 2(CO) 6 (M = Fe, Rh) and (MeC 5H 4) 2Cr 2(μ-SCMe 3)(μ 3-S) 2Co(μ 3-S) 2Fe 2(CO) 6

Abstract

Reaction of Cp 2Cr 2(SCMe 3) 2S (I) with Fe 3S 2(CO) 9 gives the novel metallospirane cluster Cp 2Cr 2(μ-SCMe 3)(μ 3-S) 2Fe(μ 3-S) 2Fe 2(CO) 6 (II). Analogous clusters with Co and Rh as central ions (III and IV respectively) have been obtained from the reaction of (MeC 5H 4) 2Cr 2(μ-SCMe 3)(μ 3-S) 2Co(CO) 2 or Cp 2Cr 2(μ-SCMe 3)(μ 3-S) 2RhL 2 (L = CO, L 2 = COD) with Fe 2(CO) 6S 2. The X-ray diffraction study of II (space group P 1 , a 9.691(4), b 12.294(3), c 14.515(5) Å, α 66.25(2), β 74.89(3), γ 78.61(3)°, V 1519.8 Å 3, Z = 2) reveals Cr 2Fe and Fe 3 triangles in the Cr 2FeFe 2 metallospirane core at a dihedral angle of 106.8°, and the geometry of dichromium disulfide thiolate fragment remains unchanged as compared to I, III and IV (CrCr 2.689; 2.610(2); 2.598(2); 2.608(5) Å in IIV, respectively). II has strong CrFe bonds (2.717(2) and 2.727(2) Å, but the two bonds between the central and peripheral Fe atoms (3.018(2) and 3.032(2) Å) are relatively weak. The peripheral FeFe bond (2.503(2) Å) is still rather short. Formal replacement of the Fe atom in II by the Co atom in III (space group Pnam, a 14.549(2), b 14.480(2), c 14.146(2) Å, V 2980.1 A 3, Z = 4) results in the rupture of the FeFe bond (Fe…Fe 3.399(2) Å) and formation of the two single CoFe bonds (2.554 (2) and 2.538(2) Å). The dihedral angle between the planes of the metal triangles Cr 2Co and CoFe 2 in III is 90°. The geometry of the Rh(S) 2Fe 2(CO) 6 moiety in the Rh-containing metall-spirane IV (space group P2 1/ n, a 9.800(2), b 12.983(3), c 22.606(5) Å, β 97.05(2)°, V 2854.3 Å 3, Z = 4) is not significantly different from that of the Co(S) 2Fe 2(CO) 6 fragment in III (RhFe 2.650(4) Å, Fe…Fe 3.344(4) Å), the main difference involves the dihedral angle between the Cr 2Rh and RhFe 2 planes, which is 129.1° in IV. This difference being due to the tendency of the Rh I atom to form the square planar complexes on one hand, and to decreasing the repulsion between the S atoms and the strengthening the RhCr bonds in the nonplanar ligand environment of the Rh atom on the other.